1. Field of the Invention
The present invention relates generally to energy dispersive analyses of intracellular mineral concentrations, and more particularly to methods for determining the concentrations of low molecular weight minerals in relatively small tissue specimens and for relating such concentrations to disease and metabolic status.
A variety of low molecular weight minerals, including calcium, phosphorus, potassium, magnesium, sodium, and chlorine, are essential for proper tissue growth, development, and functioning. Heretofore, researchers have attempted to relate serum levels of these minerals to the disease and metabolic status of patients. Serum levels of the minerals, however, are not necessarily reflective of the intracellular concentrations of the minerals at any given time. Indeed, using the methods of the present invention, it is observed that intracellular mineral levels are much more responsive to diseased conditions and other stress factors than are the serum levels of such minerals.
The determination of intracellular mineral concentrations, however, is problematic. Prior art methods, such as atomic absorption, require relatively large tissue samples in order to obtain the desired information. While such samples may be obtained by surgical techniques, such an approach is hardly desirable for routine screening of asymptomatic subjects. Some researchers have attempted to circumvent this problem by employing lymphocytes as a cellular source. The use of lymphocytes, unfortunately, is not generally useful since their intracellular mineral concentrations do not necessarily correspond to those in body tissues, and they have a large nucleus to cytoplasm ratio. Moreover, the status of the lymphocytes is greatly affected by the presence of infection, and the status of the immune response. Moreover, the lymphocyte isolation techniques seem to have an effect on the measured levels of intracellular minerals.
For these reasons, it would be desirable to provide improved methods for measuring the concentrations of intracellular minerals from relatively small tissue samples which may be obtained by non-invasive techniques. It would be further desirable that the method provide highly accurate measurement of the intracellular concentration of all minerals of interest, provide for measurement of an absolute concentration value rather than a ratio of mineral values, and provide information which may be correlated with the disease and metabolic status of the patient undergoing testing.
2. Description of the Relevant Art
Intracellular mineral concentrations have been associated with a number of diseases. Magnesium and other minerals have been related to cardiovascular disease, ischemia, cardiac necrosis, susceptibility to cardiotoxic agents, as well as having an affect on coronary blood flow, blood clotting, and artherogenesis. Seelig and Heggtveit (1974) Amer. J. Clin. Nutrition 27:59-79. Cardiovascular disease and the relationship of minerals identified by serum, blood, and tissue analysis have been reported by many investigators. See, e.g., Abraham (1977) N. Eng. J. Med. 296:862-863; Dyckner (1979) A. Heart J. 97:12-18; Whang (1981) Acta. Med. Scand. 647:139-144; Levine (1984) N. Engl. J. Med. 310:1253-1254; and Levin (1985) Cardiovascular Med. October:37-42. Hook et al. (1985) J. Am. Coll. Nutrition 4:332, Abstract 52, 26th Annual Meeting of the American College of Nutrition and the Fourth International Symposium on Magnesium, describe the use of electron probe microanalysis for the determination of magnesium in peripheral blood mononuclear cells.
The determination of intracellular magnesium/calcium ratios and the relationship of such ratios to patients with diagnosed cardiovascular disease was first reported by the inventor herein in Federation Proceedings, Vol. 42, March 1983, and at the International Symposium on Magnesium and its Relationship to Cardiovascular, Renal, and Metabolic Disorders, Los Angeles, Calif. in February, 1985. The presentation also discussed the changes in calcium and magnesium levels in athletes before and after athletic competition. A paper based on the earlier presentation was subsequently published in Magnesium: Experimental and Clinical Research, 4:210-211, November 1985.